| /* |
| * The "user cache". |
| * |
| * (C) Copyright 1991-2000 Linus Torvalds |
| * |
| * We have a per-user structure to keep track of how many |
| * processes, files etc the user has claimed, in order to be |
| * able to have per-user limits for system resources. |
| */ |
| |
| #include <linux/init.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/bitops.h> |
| #include <linux/key.h> |
| #include <linux/interrupt.h> |
| #include <linux/module.h> |
| #include <linux/user_namespace.h> |
| |
| /* |
| * UID task count cache, to get fast user lookup in "alloc_uid" |
| * when changing user ID's (ie setuid() and friends). |
| */ |
| |
| #define UIDHASH_MASK (UIDHASH_SZ - 1) |
| #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK) |
| #define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid))) |
| |
| static struct kmem_cache *uid_cachep; |
| |
| /* |
| * The uidhash_lock is mostly taken from process context, but it is |
| * occasionally also taken from softirq/tasklet context, when |
| * task-structs get RCU-freed. Hence all locking must be softirq-safe. |
| * But free_uid() is also called with local interrupts disabled, and running |
| * local_bh_enable() with local interrupts disabled is an error - we'll run |
| * softirq callbacks, and they can unconditionally enable interrupts, and |
| * the caller of free_uid() didn't expect that.. |
| */ |
| static DEFINE_SPINLOCK(uidhash_lock); |
| |
| struct user_struct root_user = { |
| .__count = ATOMIC_INIT(1), |
| .processes = ATOMIC_INIT(1), |
| .files = ATOMIC_INIT(0), |
| .sigpending = ATOMIC_INIT(0), |
| .mq_bytes = 0, |
| .locked_shm = 0, |
| #ifdef CONFIG_KEYS |
| .uid_keyring = &root_user_keyring, |
| .session_keyring = &root_session_keyring, |
| #endif |
| }; |
| |
| /* |
| * These routines must be called with the uidhash spinlock held! |
| */ |
| static inline void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent) |
| { |
| hlist_add_head(&up->uidhash_node, hashent); |
| } |
| |
| static inline void uid_hash_remove(struct user_struct *up) |
| { |
| hlist_del_init(&up->uidhash_node); |
| } |
| |
| static inline struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent) |
| { |
| struct user_struct *user; |
| struct hlist_node *h; |
| |
| hlist_for_each_entry(user, h, hashent, uidhash_node) { |
| if(user->uid == uid) { |
| atomic_inc(&user->__count); |
| return user; |
| } |
| } |
| |
| return NULL; |
| } |
| |
| /* |
| * Locate the user_struct for the passed UID. If found, take a ref on it. The |
| * caller must undo that ref with free_uid(). |
| * |
| * If the user_struct could not be found, return NULL. |
| */ |
| struct user_struct *find_user(uid_t uid) |
| { |
| struct user_struct *ret; |
| unsigned long flags; |
| struct user_namespace *ns = current->nsproxy->user_ns; |
| |
| spin_lock_irqsave(&uidhash_lock, flags); |
| ret = uid_hash_find(uid, uidhashentry(ns, uid)); |
| spin_unlock_irqrestore(&uidhash_lock, flags); |
| return ret; |
| } |
| |
| void free_uid(struct user_struct *up) |
| { |
| unsigned long flags; |
| |
| if (!up) |
| return; |
| |
| local_irq_save(flags); |
| if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) { |
| uid_hash_remove(up); |
| spin_unlock_irqrestore(&uidhash_lock, flags); |
| key_put(up->uid_keyring); |
| key_put(up->session_keyring); |
| kmem_cache_free(uid_cachep, up); |
| } else { |
| local_irq_restore(flags); |
| } |
| } |
| |
| struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid) |
| { |
| struct hlist_head *hashent = uidhashentry(ns, uid); |
| struct user_struct *up; |
| |
| spin_lock_irq(&uidhash_lock); |
| up = uid_hash_find(uid, hashent); |
| spin_unlock_irq(&uidhash_lock); |
| |
| if (!up) { |
| struct user_struct *new; |
| |
| new = kmem_cache_alloc(uid_cachep, GFP_KERNEL); |
| if (!new) |
| return NULL; |
| new->uid = uid; |
| atomic_set(&new->__count, 1); |
| atomic_set(&new->processes, 0); |
| atomic_set(&new->files, 0); |
| atomic_set(&new->sigpending, 0); |
| #ifdef CONFIG_INOTIFY_USER |
| atomic_set(&new->inotify_watches, 0); |
| atomic_set(&new->inotify_devs, 0); |
| #endif |
| |
| new->mq_bytes = 0; |
| new->locked_shm = 0; |
| |
| if (alloc_uid_keyring(new, current) < 0) { |
| kmem_cache_free(uid_cachep, new); |
| return NULL; |
| } |
| |
| /* |
| * Before adding this, check whether we raced |
| * on adding the same user already.. |
| */ |
| spin_lock_irq(&uidhash_lock); |
| up = uid_hash_find(uid, hashent); |
| if (up) { |
| key_put(new->uid_keyring); |
| key_put(new->session_keyring); |
| kmem_cache_free(uid_cachep, new); |
| } else { |
| uid_hash_insert(new, hashent); |
| up = new; |
| } |
| spin_unlock_irq(&uidhash_lock); |
| |
| } |
| return up; |
| } |
| |
| void switch_uid(struct user_struct *new_user) |
| { |
| struct user_struct *old_user; |
| |
| /* What if a process setreuid()'s and this brings the |
| * new uid over his NPROC rlimit? We can check this now |
| * cheaply with the new uid cache, so if it matters |
| * we should be checking for it. -DaveM |
| */ |
| old_user = current->user; |
| atomic_inc(&new_user->processes); |
| atomic_dec(&old_user->processes); |
| switch_uid_keyring(new_user); |
| current->user = new_user; |
| |
| /* |
| * We need to synchronize with __sigqueue_alloc() |
| * doing a get_uid(p->user).. If that saw the old |
| * user value, we need to wait until it has exited |
| * its critical region before we can free the old |
| * structure. |
| */ |
| smp_mb(); |
| spin_unlock_wait(¤t->sighand->siglock); |
| |
| free_uid(old_user); |
| suid_keys(current); |
| } |
| |
| void release_uids(struct user_namespace *ns) |
| { |
| int i; |
| unsigned long flags; |
| struct hlist_head *head; |
| struct hlist_node *nd; |
| |
| spin_lock_irqsave(&uidhash_lock, flags); |
| /* |
| * collapse the chains so that the user_struct-s will |
| * be still alive, but not in hashes. subsequent free_uid() |
| * will free them. |
| */ |
| for (i = 0; i < UIDHASH_SZ; i++) { |
| head = ns->uidhash_table + i; |
| while (!hlist_empty(head)) { |
| nd = head->first; |
| hlist_del_init(nd); |
| } |
| } |
| spin_unlock_irqrestore(&uidhash_lock, flags); |
| |
| free_uid(ns->root_user); |
| } |
| |
| static int __init uid_cache_init(void) |
| { |
| int n; |
| |
| uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct), |
| 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
| |
| for(n = 0; n < UIDHASH_SZ; ++n) |
| INIT_HLIST_HEAD(init_user_ns.uidhash_table + n); |
| |
| /* Insert the root user immediately (init already runs as root) */ |
| spin_lock_irq(&uidhash_lock); |
| uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0)); |
| spin_unlock_irq(&uidhash_lock); |
| |
| return 0; |
| } |
| |
| module_init(uid_cache_init); |